In photolithography, photoresist is used to create a pattern of layers on a substrate. Wafer processing photoresist coater modules are known in the art. For example, U.S. Pat. No. 5,911,090 to Orth describes a prior art wafer processing photoresist coater module, adapted here as FIG. 1. The prior art coater module 100 includes a substrate 102, for example a wafer, loaded on a spin chuck 104. A photoresist dispense nozzle 106 is used to dispense photoresist 108 onto the substrate 102 in the form of droplets. Photoresist dispense motor 114 drives the dispensation of the photoresist. The spin chuck 104 is rotated with a spinner motor 107 to spread and coat the surface on the substrate 102 with photoresist 108. The spin chuck 104 is also spun to distribute the photoresist cleaning solvent 110 dispensed from edge bead dispense nozzle 112. The edge bead dispense nozzle dispensation is driven by edge bead dispense (EBD) motor 120. The edge bead dispense nozzle 112 and the photoresist nozzle 106 may be disposed on a robotic arm 116 connected to a robotic arm motor 118 for positioning the arm when dispensing photoresist and photoresist cleaning solvent. Operations of the coater module are controlled by a process controller 122.
During the coating process, photoresist coating material can collect and form an edge bead along the edge of the wafer. A problem with edge beads is that they may flake and create small particles which may cause defects in the wafer. The edge bead removal dispense nozzle 112 is used to dispense photoresist cleaning solvent 110 such as an edge bead removal solvent on the wafer edge to dissolve the edge bead.
Another common cause of defects and variability in photoresist coatings is the tendency of photoresists to dry rapidly and to form residues on the photoresist dispense nozzles. These residues can obstruct an orifice of the photoresist dispense nozzle which affects the amount and way in which the photoresist is dispensed. Particles of dried photoresist formed from the photoresist solution on the nozzle may contaminate the photoresist solution or fall directly onto the substrate. It is thus important for photoresist dispense nozzles to remain free of dried photoresist particles.
The following are some known photoresist dispense nozzle cleaning methods and systems. U.S. Pat. No. 7,879,152 to Lee discloses an apparatus for cleaning pollutant of the nozzle comprising a nozzle in a polluted state, a nozzle cleaning unit to clean a pollutant material from the nozzle by use of an absorbing member, and an absorbing member cleaning unit to clean a pollutant material from the absorbing member.
U.S. Pat. No. 7,891,365 to Hirao et al. discloses a nozzle cleaning apparatus and a nozzle cleaning method with the apparatus including a nozzle accommodated in a cleaning container having a funnel shaped portion. In the method, a cleaning solvent is supplied along an inner surface of the funnel shaped portion. The solvent forms a whirling vortex flow around the nozzle for cleaning.
It is an objective of the present invention to provide new and improved methods and systems for cleaning a photoresist dispense nozzle.